The present invention concerns protective elements for making an add-on reactive armour mounted on the outside of a land vehicle liable to be exposed to attack by projectiles with shaped charge munition, e.g. a tank, an armoured car and the like.
Projectiles with shaped charge munition, also known as hollow charge munition, are known to pierce armour and thereby destroy the protected object from within. This capacity of a shaped charge results from the fact that upon detonation there forms an energy-rich jet also known as "thorn" or "spike" which advances at a very high speed of several thousand meters per second and is thereby capable of piercing even relatively thick steel walls, such as are used in armoured vehicles and tanks.
In U.S. Pat. No. 4,368,660 there is described an arrangement which purports to afford protection against the penetrating effect of an exploding hollow charge. According to that proposal there is provided a continuous wall structure having an explosive layer sandwiched between two wall members of an inert material, e.g. a metal, and being so arranged that the axis of an impinging projectile and of the thorn formed upon detonation, includes with the surface of the wall structure an acute angle of say 45.degree.. According to said U.S. patent, when a hollow charge projectile hits the upper surface of such a protective arrangement and the explosive layer detonates, the walls thereof are thrown in opposite directions, one moving away from and the other one in the direction of the protected substrate. In consequence and due to the angle included betwen the thorn and the wall surface, the thorn is successively intersected by different portions of the wall members with the consequence that the energy of the thorn is rapidly consumed.
A similar arrangement is disclosed in British patent specification No. 1,581,125 with the sole difference that in accordance with that disclosure the arrangement of the layer of explosive substance may optionally be covered only on one side by a layer of a non-combustible material.
The theory put forward in both the said U.S. and British patent specifications is basically sound but in practice it has been found that arrangements disclosed therein are inoperable.
For one, it follows from the disclosure in the specifications of these patents that the protective arrangement is mounted directly on the substrate to be protected. In consequence the rear wall of the arrangement, i.e. the one that bears on the substrate, is virtually immobile and cannot move anymore towards the substrate. Consequently the rear wall is prevented from participating in the reduction of the energy of the thorn. Furthermore, where the protective arrangement is continuous as stipulated in the claims of U.S. Pat. No. 4,368,660, there occurs a so-called sympathetic initiation, meaning that where the explosive charge is detonated at the site that is hit by a hollow charge projectile, this detonation spreads in all directions with the consequence that the entire protective arrangement or a significant part thereof is destroyed by one single hit. An arrangement with such properties is obviously of no practical value because in combat an armoured vehicle or tank must be capable to absorb severeal hits and accordingly the arrangement should be such that upon each hit only a restricted area around the hit site is destroyed while the remaining protective arrangement remains intact. A similar sympathetic initiation also results where the protective arrangement is applied to the walls of a vehicle in the manner of roofing tiles as mentioned in column 3 lines 48 and 49 of the U.S. Pat. No. 4,368,660 it is inherent in a roofing tile arrangement that the individual members overlap.